Mathematics
by Blind Author
Summary: It isn't bravery that makes John so willing to risk his life for Sherlock. At least, he doesn't think it is – it's just simple mathematics. John/Sherlock implied, Reichenbach spoilers.


**Disclaimer:** I do not own Sherlock – the characters or the setting – and am making no profit from their use.  
**Warnings:** Self-esteem issues, Reichenbach.

**Spoilers: **All of season 1 and 2.

**Mathematics**

John is shot when a sniper starts picking off his squad and he bends over his patient to shield him. It can't be said to set a precedent, because that would imply he hasn't done that sort of thing before.

xx

It's not that John shot the cabbie without thinking about it – he did think about it, very carefully in fact. He was just able to think _quickly_, because the whole thing was very simple; it was the only way to save Sherlock's life.

And even if John had gone to jail for it, well, he could have lived with that. Because Sherlock is amazing and _brilliant_, and he makes the world a better place – maybe not a politer or gentler place but still _better_ – and John's a washed-up army doctor who happens to be good with guns. John is quite certain he's not making the world a better place.

It's simple mathematics. That's how he sees it in his head, complete with that little arrow symbol that means 'greater than' or 'less than' depending on which way it's pointing.

_Sherlock Holmes life is greater than John Watson's reputation._

It's simple mathematics.

xx

John's quite pleased he came off worst in their struggle with the Black Lotus. He's got a concussion, a cracked rib and a gash on the side of his head that just won't stop bleeding. Meanwhile, Sherlock and Sarah are walking away with a couple of bruises and abrasions.

"Everything worked out alright then," he sighs, grimacing as he holds the bag of cold peas against his head – he really needs to buy a proper cold pack at some point.

"This is your definition of 'alright'?" Sherlock snarls. "They could have killed you."

John has taken off his bloodstained shirt and left it draped over a kitchen chair, and Sherlock is staring at it like he thinks he can will John's injuries out of existence if he just focuses hard enough.

John shrugs. "You and Sarah weren't hurt – I'll call that win."

He has no idea why Sherlock scowls so viciously at this – doesn't he get it?

_Sherlock and Sarah's safety is greater than John's safety._

Really, it's not difficult.

xx

After Moriarty, John doesn't want to do anything except collapse and attempt to sleep the trauma away. So of course, that's the one thing Sherlock won't let him do.

"What did you mean when you told me to run?"

"Exactly what I said," John groans from where he's lying on the couch – he's not up to another flight of stairs right now. "For you to run away from the bomb and snipers like a sensible person. I suppose I should have known better."

"You actually intended for me to abandon you?"

Sherlock sounds so offended John actually raises his head to track his friend's pacing. "That _was_ the idea."

Sherlock gives him a glare almost as fierce as the one he'd turned on Moriarty. "He would have killed you!"

"Yeah, no shit," John mutters; he's really too tired to deal with this. "But hey, better me than you, right?"

He doesn't know why Sherlock looks so stricken – it's really very simple.

_Sherlock Holmes life is greater than John Watson's life._

Basic mathematics.

xx

John doesn't like Irene. She's playing Sherlock like a master con artist, and in the end, she's going to serve her own interests rather than help or protect Sherlock. And Sherlock either doesn't notice or doesn't care.

The former, John can understand – for all his deductions, Sherlock isn't exactly well-versed in discerning people's motives. The latter…actually, John can understand that too. Sometimes you just can't help caring for someone you know is going to hurt you – right now, that's John's whole world in a nutshell.

But it isn't purely jealousy that drives John out the flat when he leaves that night. It's much more elemental than that.

_Sherlock's happiness is greater than John's feelings_

It's simple, really.

xx

On the rooftop of a hospital, Sherlock discovers that just because you've planned for something doesn't mean you won't be scared. Because he is scared – in this one moment, he is more terrified than he's ever been in his life. There are so many ways this could go wrong, some part of him is tempted to just call it all off…

But he can't. Because standing on the pavement below him is the person who taught Sherlock what it meant to have something to lose, and if he doesn't fall, John Watson is going to die. And a world without John is the worst hell Sherlock can conceive of.

He needs to protect John because John makes the world a better place. He needs to protect John because John always, _always_ protects him and now it's Sherlock's turn.

He needs to protect John because John never protects himself.

_John's life is greater than Sherlock's life._

But that's not quite all of it, is it?

_John's life is greater than everything else._

It's simple mathematics.

xx

_AN: Thanks so much to my beta, ginbitch!_


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